1. Field of the Invention (Technical Field)
The present invention relates to methods, software, and apparatuses for distinguishing between rain and potential targets in Doppler radar systems.
2. Description of Related Art
Rain return obscures Doppler radar screen and airborne target detection by increasing the number of false targets detected. For example, a serious problem with Fire Control Radar is in experiencing an increase in false target (e.g., helicopter) detections in severe wind driven rain. Returns from rain are similar to those from true targets in width, shape, and frequency. Typical Constant False Alarm Rate (CFAR) processing has attempted to discriminate against rain and targets with a series of thresholds operating upon the radar information (including the rain energy). With this limitation the demands upon the CFAR to maintain a fixed false alarm rate requires more stringent thresholds thus reducing the detection capability of the system.
The present invention provides an advanced digital signal processing method, apparatus, and software to effectively remove/filter rain energy/signal from the radar data utilizing the logic of recognizing the extent of rain in both range and Doppler (as compared to the limited extent of a airborne target), and substituting with thermal noise. This allows the subsequent classical CFAR processing to operate with lower thresholds (increasing target detectability) while maintaining the required false alarm rate. Targets can then be detected as easily in rain as in clear conditions. A technique of this type is novel in that, among other considerations, the rain energy is actually removed from the radar data enabling subsequent detection processing to be performed without rain considerations.